The present invention relates to a liquid pressure measuring system. Particularly, to a system for non-destructively measuring fluid pressure from outside the body containing the fluid, by the use of ultrasonic waves. For example, blood pressure in the heart of a living body or the pressure of flowing liquid used in the chemical industry to show particularly high temperature and pressure, the high probability of a chemical reaction or the existence of solid particles or fibres etc., in cases where it is difficult to insert a pressure gauge directly into a measuring object.
Currently, a catheter equipped with a pressure sensor has been inserted into the blood vessels or heart in order to measure blood pressure. This method is accompanied by the disadvantages of creating pain and a risk to life by the unexpected misoperation or by infection. The methods of acoustically detecting a blockage of the blood flow in the arm or detecting the start of a pulse by winding a cuff around the arm and changing the air pressure are also known. This method using a cuff can be applied to the arms and legs but cannot be used for measurement of internal organs such as the heart.
In the field of industrial systems operating at a high temperature, a low temperature, and/or in a strong radiation field, and the handling of liquids which are chemically active, of high viscosity, or of a dense mixture of grain particles, chips of wood and fibres etc. pressure sensors have often been damaged by temperature, radiation, chemical reaction or by external force due to solid materials. Therefore, it is desired to measure pressure from outside of a vessel or system but there has been no adequate method.